1. Field of the Invention
The present invention relates to a lighting apparatus and a display apparatus, having the same, suitable as a lamp for illuminating automotive meters, alarm lights, and the like.
2. Prior Art
Conventionally, the lamp socket described in Japanese Utility Model Publication No. HEI 7-22068 (hereinafter referred to as the prior art 1) and a light-emitting diode assembly described in Japanese Utility Model Publication No. HEI 6-17326 (hereinafter referred to the prior art 2) are known as examples of the sockets of the display lamps for the automotive meters, alarm lights, and the like.
The prior art 1 provides a structure in which a lamp socket with an incandescent lamp mounted is inserted into an insertion hole of a printed circuit board to be mounted on the printed circuit board. Because the light source is an incandescent lamp, however, various problems are posed in service life, brightness, temperature, etc., and a maintenance-free configuration is difficult to realize.
In contrast, the prior art 2, which uses a light-emitting diode (hereinafter referred to as LED) having a long service life and high brightness and being superior in cold and heat resistance as a light source, can realize an improved maintenance-free configuration.
The LED has polarities, and therefore, in assembling a pair of contact terminals on a lighting circuit board with the LED mounted thereon, stepped portions of different sizes are formed at the transversely opposite positions of the leading ends of the band-shaped lead pair of the contact terminals so as not to select a wrong polarity, and a pair of mounting holes of the lighting circuit board into which the leading ends of the leads are inserted also have different sizes.
In this prior art 2, however, a fine machining process is required for forming the stepped portions in transversely opposite and different shapes corresponding to the polarities of the LED at the leading ends of a pair of fine leads of the contact terminals. Further, the lead of each contact terminals is so small that it cannot be easily machined, resulting in the problem of low machining workability.
FIG. 11 shows an arrangement of a conventional structure, in which a light emitting diode 1 and a lighting circuit board 3 connected through a pair of lead frames 2a, 2b of the LED 1, which are bent into L-shape. The horizontal portions of the L-shape are inserted through a pair of mounting holes 3a, 3b of the lighting circuit board 3, and the leading ends thereof passing through the holes are fixed by a solder 4 for establishing an electrical and mechanical connection between the LED 1 and the circuit board 3, according to such structure, the center axis Oa of the LED 1 is offset from the center line Ob of the lighting circuit board 3, that is, the center line of the circuit board 3 does not accord with the center axis of the LED 1 in the direction along the thickness of the light circuit board.
As a result, the lower end portion 1a of the LED 1 in the drawing and the insertion hole of a socket body not shown in which the whole of the circuit board 3 is to be inserted become asymmetric. For this reason, the socket body cannot be easily molded, and a die for molding the socket body is complicated, which results a problem of increased cost.
Furthermore, in the use of the LED as mentioned in the above prior arts, since the LED is turned on in a normal manner, it is difficult to clearly inform a user, such as driver of an automobile, of the fact that a certain trouble or inconvenience is caused because, in one reason, an alarm or caution cannot be displayed through a flickering manner of the lighting apparatus.